Gas-cooled electrical machine having an axial fan

Abstract

In a gas-cooled electrical machine having an axial fan ( 12 a ) and a downstream guidance mechanism, arranged downstream of the axial fan, in order to raise the pressure of a cooling gas, the cooling gas is driven in a forced manner by means of the axial fan from an inlet area ( 41 ), which is bounded by an inner casing ( 21 ) and a partition wall ( 20 ) arranged in the radial plane of the axial fan ( 12 a ), into an outlet area ( 42 ) which is bounded by the partition wall ( 20 ) and an outer casing ( 37 ). In this case, the downstream guidance mechanism is designed as a deflection diffusor ( 36 ) in order to deflect a cooling-gas flow ( 39 ) from an essentially axial flow direction to an essentially radial flow direction.

What is claimed is:  
     
       1. Gas-cooled electrical machine, comprising: 
       an axial fan, an upstream guidance mechanism and a downstream guidance mechanism, arranged upstream and downstream of the axial fan, respectively, in order to raise the pressure of a cooling gas, in which case the cooling gas can be driven in a forced manner by means of the axial fan from an inlet area, which is bounded by an inner casing and a partition wall arranged in the radial plane of the axial fan, into an outlet area which is bounded by the partition wall and an outer casing, wherein the upstream guidance mechanism is designed as a diffusor in order to deflect a cooling gas flow from essentially a radial flow direction to an essentially axial flow direction and the downstream guidance mechanism is designed as a deflection diffusor in order to deflect a cooling-gas flow from an essentially axial flow direction to an essentially radial flow direction.  
     
     
       2. Gas-cooled electrical machine according to  claim 1 , wherein the deflection diffuser comprises a diffusor funnel and a diffusor wall, the diffusor funnel is arranged with its small funnel opening against the partition wall, and the diffusor wall is arranged on a large funnel opening of the diffusor funnel, whereby the diffusor wall has an inner radius on the large funnel opening, and furthermore the diffusor wall extends between the inner radius and an outer radius. 
     
     
       3. Gas-cooled electrical machine according to  claim 2 , wherein the diffusor wall is designed in an annular shape and is arranged parallel to the outer casing at an axial distance. 
     
     
       4. Gas-cooled electrical machine according to  claim 2 , wherein the diffusor wall is designed in the shape of a conical envelope, such that the outer radius of the diffusor wall is at a shorter distance from the outer casing then its inner radius. 
     
     
       5. Gas-cooled electrical machine according to  claim 2 , wherein the outer radius of the diffusor wall is less than twice its inner radius. 
     
     
       6. Gas-cooled electrical machine according to  claim 2 , wherein a number of guide vanes are arranged between the diffusor wall and the outer casing. 
     
     
       7. Gas-cooled electrical machine according to  claim 2 , wherein the diffusor funnel has a funnel radius, which funnel radius is greater than 0.6 times a channel height of a flow channel, which flow channel is formed between the partition wall and a rotor shaft the electrical machine. 
     
     
       8. Gas-cooled electrical machine according to  claim 7 , wherein the distance between the outer radius of the diffusor wall and the outer casing is about 0.78 to 0.9 times the channel height of the flow channel. 
     
     
       9. Gas-cooled electrical machine according to  claim 7 , wherein the inlet area between the inner casing and the partition wall has a width, in which case the width is greater than 1.8 times the channel height the flow channel. 
     
     
       10. Gas-cooled electrical machine according to  claim 1 , wherein cooling gas which has been heated is sucked outside of the partition wall by the fan.